X-101-D or similar restoration thread

[oldman55]

I have searched this forum and cannot find a restoration thread for a X-101-D. From reading other threads in this forum, it seems like there are some mods in the output stage that are helpful for both sonics and longevity. IBAM or other circuitry changes will also be required to bias each tube individually and I was hoping to find some details for these mods.

What other Fisher units are similar to the X-101-D and may be helpful?

Thanks all.
Oldman

 

[thornev]

Hey Oldman. Have you checked out the stickies? http://audiokarma.org/forums/index.php?forums/fisher-forum-stickies.210/

IBAM is applicable to several Fisher units. Study the circuitry and apply the principles to your 101-D. Maybe you can make it work. I bet someone with more experience will join in and give you better info.

Thorne

 

[bhamham]

Here's a couple of good threads on restoring the X-101-C, circuits are probably similar:

http://www.audiokarma.org/forums/index.php?threads/fisher-tube-chassis-balance-controls.654505/
http://www.audiokarma.org/forums/index.php?threads/improving-the-fisher-x-101c.582379/

 

[Catmanboo]

X-101-d's are relatively rare, not even a Sams manual on 'em that I know of. Fisher gear using 7591's are pretty much similar at the ouput stages so the info in the stickies as mentioned by @thornev will set you straight. I have one of those myself, $5 flea mkt find from long ago. Looked like it lived in a maggot wagon (garbage truck) when I got it. Had to refinish the cabinet just to be able to look at it. Chassis looks like crap still, but it works, need to do the mods on it someday. Good luck, read & learn!

 

[larryderouin]

HIFI ENGINE has the FISHER manual for it. I sent it to FISHERCONSOLES so Jon could include it there.

 

[Catmanboo]

You da man, Larry! Tnx, & happy sunday morning to you!

 

[oldman55]

Thanks all for the help.
I think from the 101-C threads, I have a pretty good handle on it. I compared the schematics and they are fairly similar. Dont quite have the bias supply figured out yet though. Or adjusting the inverters with a scope either.
Took a bit to come up with a good B+ PS can solution and should work if starting off with 250ufs in the doubler circuit in lieu of 200uf is ok (can also tie together some 100/100/500v cans together for the 200uf if its not).
Oldman

Edit: Since the rectifiers are silicon and measure well, I assume there is no need for replacing?

 

[larryderouin]

250uf in the doubler can's is ok. I would tend to go up in Voltage 50-100V due to variances in Line Voltage from 1965 to now. Keeps the Surge Voltage to a Mild Roar and below the can's max rating.

If they measure good use them, but they are 53 years old, and 1n5408's and 1n4007 are cheap insurance.

 

[oldman55]

Would be:

200uf/300v to JJ200uf/475v;

40uf200v to JJ 250/500v and 40uf/525 from next can

40/40/20/475v to CE 40/40/40/40/525v using last 40uf for above

Seems the cleanest way to go for me without any chassis changes (except maybe a clamp on the JJ)

With cathode bias, is there any way to add a 1ohm cathode resistor into the mix where they go to gournd?
Oldman

Diodes - just trying to keep the unit as original looking as possible but have some I could always add.

250uf in the doubler can's is ok. I would tend to go up in Voltage 50-100V due to variances in Line Voltage from 1965 to now. Keeps the Surge Voltage to a Mild Roar and below the can's max rating.

If they measure good use them, but they are 53 years old, and 1n5408's and 1n4007 are cheap insurance.

 

[larryderouin]

Get hold of TOM @ Hayseed Hamfest. They can build Can caps that exceed spec's and voltage and no mods needed. And it would be slightly less than the CE and JJ's combined. Plus rated for 105*C.

You can put them right off the tube in series @ pin 5 just like a fixed bias.

 

[oldman55]

Get hold of TOM @ Hayseed Hamfest. They can build Can caps that exceed spec's and voltage and no mods needed. And it would be slightly less than the CE and JJ's combined. Plus rated for 105*C.

You can put them right off the tube in series @ pin 5 just like a fixed bias.

And I thought that I had a pretty good solution on the can issue and thought for about 50 bucks less than Hayseed. Regardless, it may be $ well spent to have all twist lock with exact voltages.

If I add a resistor in series at each tube in the loop, it will have an accumulative affect when it gets to the end of the line by having 4 resistors in series.

 

[oldman55]

.

 

[oldman55]

.

 

[larryderouin]

1 ohm or 10 ohm will have an extremely negligible effect on Cathode Voltage. Remove the lead from pin 5 and put the resistor in place of the lead, then attach the lead to the free end of the resistor. The only in series is at each tube, not in the common buss line. (see jpg)

 

[oldman55]

1 ohm or 10 ohm will have an extremely negligible effect on Cathode Voltage. Remove the lead from pin 5 and put the resistor in place of the lead, then attach the lead to the free end of the resistor. The only in series is at each tube, not in the common buss line. (see jpg)
View attachment 1446993

Is that an error in the schematics that shows one cathode as pin 5 and the other cathode as pin 3? Or am I reading something wrong?
Oldman

 

[larryderouin]

It's an error. Both of the lower tubes have pins 3 and 5 mis numbered. This is one of the FEW that FISHER made. And I say FEW as compared to SANSUI's TSUNAMI worth of errors in their schematics/parts lists, FISHER's is just a slight ripple.

 

[oldman55]

After reviewing all of the 101-c and d threads I could, I compiled the following recommended simple mods for the x101d:

Bump the doublers to 220uf from 200uf
Add 100 ohm screen resistors
.1 coupling caps and grid resistor change to 220k
install cathode measuring resistors
add cl-80s
possibly replacing diodes

I dont understand the adding of a 10k bias pot as there is already a bias adj pot. Am I missing something here? Or any other mods?

oldman

 

[larryderouin]

Change the coupling caps to .068uf. This and the 220K resistors make the R/C timing almost identical to the original timing using .047uf and 330K resistors.

I think the 10K pot will allow you some more fudge room if using Tung-Sol Re-Issues as they tend to run "HOT" at normal bias voltages. for example to get 32ma, a EH7591 or old stock Westie uses about -18V to -19v while the T-S needs approx -21v to -22v. But I could be wrong in my presumption. I'll need to look thru the threads.

 

[oldman55]

Change the coupling caps to .068uf. This and the 220K resistors make the R/C timing almost identical to the original timing using .047uf and 330K resistors.

Dont know where I got the .1uf. Any way to change the resistor even more to make timing the same with .1uf coupling caps (put in an order with upgraded coupling caps)?
Also, any advantages to changing any other PS cap values?
oldman

 

[oldman55]

My 101d was mainly untouched except for a changed diode. In the process of putting it in, there was apparently a modification for its installation.
Wonder why this one wire was cut and how it originally was wired?

If anyone has a x101d (or x101c) open, or a photo of this area on file, it would be appreciated.


Thanks all
Oldman55